Electric vehicles (EVs) and grid-scale energy storage are both necessary components of a future society with significantly reduced carbon emissions. Grid storage, and especially EVs, depend on rechargeable batteries to function. To further improve these technologies, the field seeks to increase the energy density, improve the power performance (how fastbatteries can charge and discharge), and decrease cost of Li-ion batteries (LIBs) without sacrificing long term cycle life. It is unlikely that all of these desirable qualities can be found in a single new LIB electrode material; the needs of the future require that we diversify. New, high-voltage LIB cathode materials can help improve the energy density of the overall cell. Electrode materials allowing faster transport of both Li+–ions and electrons can allow a cell to cycle more quickly without losing accessible capacity. Finally, a main contributor to the high cost of LIBs is the scarcity (and supply chain) of certain necessary elements: Li, Co, and Ni. Improved LIB recycling procedures could reduce the cost of LIBs in the future when these elements become even more scarce. Better yet would be utilizing novel battery materials which rely on less–scarce elements.
In the following chapters, I discuss improving the energy density, power performance, and recyclability of LIBs from the angle of structure-property relationships of the atomic-level crystal structures in electrode materials. I will briefly mention how successfully computation can be employed to predict different electrode characteristics. Specifically, I evaluated Li5VF4(SO4)2 and three compositions of lithium copper phosphate as high-voltage cathode materials, and various reduced Mo oxides as fast charging electrodes. I prepared these active materials (and many more) using air-free, solid-state techniques, and then incorporated them into both thick film electrodes and slurry-cast thin film electrodes. I used the electrodes to build Li half-cells and evaluate the electrochemical performance of new materials using techniques such as cyclic voltammetry, galvanostatic intermittent titration, and galvanostatic cycling at varying rates. I also used operando X-ray diffraction and ex situ X-ray photoelectron spectroscopy to study how the structure and oxidation states of these active materials changed during battery cycling. Finally, I used many elemental and phase analysis techniques to investigate the composition of a heat-treated LIB recycling feedstock to inform improvements to industrial hydrometallurgical battery recycling processes. Throughout my work, I discuss the trade-offs between redox voltage, capacity, and conductivity in LIB electrodes, and how changing coordination environments around the redox metal affect long term cyclability.